This invention relates to wireless communication and, more particularly, to techniques for effective wireless communication in the presence of fading, co-channel interference, and other degradations.
A significant body of information relating to this disclosure can be found in the aforementioned U.S. Patent ""908, ""838, and ""494 applications. These applications are, therefore, hereby incorporated by reference in order to shorten the exposition of this invention. Some of this information, however, is summarized below.
In U.S. application Ser. No. 09/074,224 titled xe2x80x9cTransmitter Diversity Technique for Wireless Communication,xe2x80x9d now U.S. Pat. No. 6,185,258, Alamouti introduces a transmit diversity scheme for two transmit antennas with a corresponding decoding algorithm that is very simple. The notions introduced by Alamouti were extended and generalized by Calderbank et al in the aforementioned ""908 application. In that disclosure, data is encoded using space-time block codes with orthogonal structures. The encoded data is split into nT streams and nT symbols are transmitted simultaneously using nT antennas. The received signal is the superposition of the nT transmitted signals, perturbed by noise. The orthogonal structure of the space-time block code allows the use of a simple decoding algorithm by decoupling of the signals transmitted from the different antennas. Space-time block codes are designed to achieve maximum possible diversity of order nT nR for nT transmit antennas and nR receive antennas, under the constraint of having a simple decoding algorithm. However, space-time block codes are not designed to, and do not achieve coding gain.
It was realized later that such gain may be realized by concatenating an outer code to the space-time coding. Indeed, in the aforementioned ""838 application, a system is disclosed with increased system capacity and improved performance that are attained by using a concatenated coding scheme where the inner code is a space-time block code and the outer code is a conventional channel error correcting code. As disclosed in that application, information symbols are first encoded using a conventional channel code and the channel encoded signal is then encoded using a space-time block code. The result is transmitted over the nT antennas. At the receiver, the inner space-time block code is used to suppress interference from the other co-channel terminals and soft decisions are made about the transmitted symbols. The channel decoding that follows makes the hard decisions about the transmitted symbols.
Disclosed is an arrangement where a turbo TCM code is concatenated with a space-time code, forming an outer code. The signal is decoded by employing a MAP decoder followed by a turbo decoder.